Natural gas well heater



-NOV- 14, E. c THRUPP NATURAL GAS WELL HEATER Filed July 6, 1951 3Sheets-Sheet l JrzuenZ-ar j- 4 3 2 I 2 4 El 2 MEL 0 6 i q J n 11'. 9 5 1m MwMnLF LT .JW a I T E1 w ji I T41]. m J "A: a M. u g v l H n W m r hmL NOV. 14, 1933 Q THRUPP 1,934,955

NATURAL GAS WELL HEATER Filed July 6, 1951 3 Sheets-sneet 2 Hlllllllllllllllllllfi Nov; 14, 1933. E. c. THRUPP 1,934,955

NATURAL GAS WELL HEATER Filed July 6, 1931 3 Sheets-Sheet 3 3/ 23 T -76f 7 5 4C 73 33 Z ,30 a 37 r 4 so 1 1: g I z o... iQ-70 Fla/2 c Fla/3 fi(g 33 H018 (Z368 I? I FIG/9 3 l3 H620 Fla/5 FIC./|4

Inventor Patented Nov. 14, 1933 UNITED STATES PATNT QFFICE 1,934,955NATURAL GAS WELL HEATER Edgar Charles Thrupp, Vancouver, BritishColumbia, Canada 4 Claims.

111 issuing into the well, by the action of the gas which issued earlierhaving cooled the strata surrounding the well. The result of thiscumulative cooling action (which is similar to that used in well knownapparatus for liquefying gases) is to 1-5 freeze any moisture which mayhappen to be present in the gas, if the gas pressure in the strata ishigh enough to produce that effect, and the ice so produced sometimesblocks up the passage in the well and the interstices of the strata,

:29 and reduces or stops the production of gas or oil.

The cooling effect of the gas expansion is modified by the heatcontained in the accompanying oil, and if the ratio of oil to gas ishigh enough, the temperature will not fall to freezing point.

125 This condition may be expected to occur with a ratio of one pound ofoil to less than three pounds of gas. I

It is the main object of my invention to supply sufficient heat in thewell to counteract .the cool- 130 ing action of the expanding gas whenthe ratio of the weights of gas to oil is more than three to one, and toconcentrate the supply of heat chiefly to that part of the well which issituated in the strata from which the gas issues.

Hitherto troubles due to freezing, such as described, have been dealtwith by firing shots of explosives in the boreholes to dislodge thefrozen strata around, or by drilling again through the ice and employingtools to remove the material, or by putting back pressure on the well toreduce the cooling by expansion. These methods are crude andunscientific, interrupting the operation of the well, are sometimes onlytemporary in their results, and may do permanent harm to the well.Several methods have been adopted for heating oil wells which havebecome incrusted with a coating naphtha. These have involved the use ofsteam, burning oil jets, electric glow bars in closed tubes, andelectric currents passed to earth. None of these are suitable fordealing with freezing troubles a mile below the surface.

The present invention is intended (for use particularly in gas wells) tosupersede all these methods by providing a hot column or cable in thatpart of the well where the cooling occurs,

and constructing that column in the form of a plurality of statictransformers supplying a large amount of current to a secondary circuitsystem at a very low voltage, usually about three or four volts, underconditions permitting the exposure of the heated circuits direct to thegas carrying a spray of oil, which helps to maintain the insulation andprevent any appreciable leakage to earth away from the place where theheat is required, or corrosion of any points of 55 contact with theearth. i

To accomplish these results I employ analterhating current ofelectricity conveyed down the well to the gas-bearing strata by a pairof insulated conductors of low resistance, such as those 7 used forunderground electrical supply cables, and through the borehole in thegas bearing strata by conductors forming the primary circuit of anelongated static transformer constructed preferably with a'circularcross section having an external diameter considerably less than thediameter of the borehole, to leave space for the passage of gas and oilout of the well. I

The primary circuit may consist of one complete turn in thetransfor'mer,or it may have two, three or more turns. The primary circuit issurrounded by a core of laminated iron sheets arranged to give amagnetic flux circuit similar to that used in ordinary transformers forelectric lighting purposes, but the core is divided into unit sectionsto servea plurality of secondary circuits. Usually a large number ofsecondary circuits will be required, each secondary circuit being servedby a short length of the primary circuit with its enclosing magneticcore.

The secondary circuits passing through the core may have one, two ormore turns, but the usual construction will have only one turn passingthrough the core with terminals brought out to the circumference of thecore or its covering. The remainder, or external parts of the secondarycircuits carrying a current of low voltage to produce heat, arearrangedon the circumference of the transformer by connecting tolongitudinal wires forming an outer protecting shield to thetransformers and also assisting the primary conductors in carrying theweight of the whole transformer when suspendedin the Well. Thelongitudinal wires are spaced apart and insulated from one another forthe greater part of their length, but are connected at certain points inzig-zag fashion to provide a network circuit of the required length fromone terminal of the internal (or generating part) of the secondarycircuit to the other terminal thereof.

The pair of low resistance conductors above the gas-bearing strata maywith advantage be enclosed in steel armoured tape or wire to make acable of considerable tensile strength to carry its own weight and thatof the transformer section below.

Passing the cable into the well against gas pressure is done throughsuitable stufiing boxes provided on top of the well casing, and thisstuffing box structure at the well head is another object of theinvention.

For convenience the whole cable is wound on a drum mounted on an axleand arranged so that the terminals of the insulated conductors can beconnected to the source of supply of electricity without unwinding thecable completely off the drum when a sufficient length is lowered intothe well. Some means of regulating the supply of current to the cable isdesirable because there may be a difficulty in estimating the exactamount of heat required, and fluctuation in the gas flow may occur.

An alternating current supply from some central source at constantvoltage may be used, and the regulation done by using an alternatingtransformer with the primary circuit divided into several sections, someof which can be switched out of action when not required.

The dimensions of the conductors and the quantity of heat to be supplieddepend upon the pressure under which the gas issues from the strata andon its volume. In round numbers the leading data are that the drop intemperature is about half a degree Fahrenheit for each atmosphere ofpressure, or 50 degrees for 100 atmospheres, and one pound weight ofaverage quality of natural gas will occupy about twenty cubic feet atordinary atmospheric pressure, and will have a specific heat about 0.60.One million cubic feet of gas will therefore weigh about 50,000 pounds,and will require, 1,500,000 British thermal units to raise itstemperature 50 degrees Fahrenheit.

Each million cubic feet ofgas issuing in 24 hours will therefore requirethe thermal equivalent of about 25 horse power to completely counteractthe cooling effect of expansion from 100 atmospheres pressure, but someof that heat will naturally come from the strata round the well and fromthe oil issuing with the gas, which may have a normal temperature ofabout 150 degrees Fahrenheit before coming to the well, so the quantityof heat to be supplied by electricity to prevent the temperature fromfalling below 32 degrees Fahrenheit, (the freezing point of water) maybe considerably less than the equivalent of 25 horse power per millioncubic feet of gas per day under the conditions named. When the stratasurrounding the well have been lowered to about 32 degrees Fahrenheit,the issuing gas will tend to drop another 50 degrees and escape at atemperature near 20 degrees below zero. These are the conditions whichhave been observed when troubles have arisen from ice blockingboreholes. The working temperature of the external secondary circuit inthe well to convey the necessary heat to the gas will usually besomewhere between 200 and 600 degrees, but no definite limit should belaid down, because special conditions may be met which can be dealt withby this invention with temperatures outside these limits. The drawingsherewith will, however, be more readily understood when it is explainedthat they are intended to apply to apparatus working at a temperaturenot exceeding 600 degrees Fahrenheit.

I will now describe my invention with reference to the drawings.

Fig. 1 is a general schematic diagram of the apparatus, which cannot beshown clearly on a single scale drawing owing to the parts extendingover several thousand feet.

Fig. 2 is a section of the stuffing boxes at the well head and the clamp(partly in elevation) used to hold the suspended transformer structurein position when lowered to the operating depth.

Fig. 3 is a plan view of the top of the clamp shown on Fig. 2.

Fig. 4 is a section of the construction at the lower end of the twinconductor cable where the conductors are connected to the turns of theprimary circuit of the transformer structure below.

Fig. 5 is a plan view at line 5, 5 in Fig. 4 of a porcelain support tothe upper end of one of the transformer primary circuit turns, withpassages for the other primary conductors.

Fig. 6 is a similar plan view of the poreclain support to anotherprimary circuit turn situated below the one shown on Figs. 4 and 5.

Fig. 7 is a vertical section of one of the transformer units with aportion of another unit below. This section is taken on the line '7, 7,in Figs. 8, l0, and 11.

Fig. 8 is a horizontal section at the centre of one of the transformerunits at the line 8, 8, in Fig. 7.

Fig. 9 is an elevation of a portion of the external secondary circuitnetwork which forms the heating element exposed to the gas.

Fig. 10 is a part plan on line 10, 10 of Fig. '7 showing the method oftying in the wires of the external secondary circuit network to thecircular shape near the points of connection to the terminals of theinternal secondary circuit.

Fig. 11 is a plan of the construction of the internal secondary circuitat the base of one of the transformer units at line 11, 11 of Fig. '7.

Fig. 12 is a half vertical section of the details of the clamping devicefor thrusting the transformer structure into the well head stuilingboxes, which is shown schematically in Fig. l, and is taken on the line12, 12 in Fig. 14.

Fig. 13 is another vertical half section of the same clamping devicetaken at right angles to the view in Fig. 12 and on line 13, 13, in Fig.14.

Fig. 14 is a plan of the same clamping device shown partly in plan atthe top of the clamp, and partly in section at the middle of the clamp,or in plan at the top of Figs. 12 and 13 and on the line 14, 14, inFigs. 12 and 13.

Fig. 15 is a diagrammatic vertical view of the construction at the lowerend of the transformer structure showing the relative positions of thethree primary circuit turns.

Fig. 16 is a plan of an insulator block situated below the lowesttransformer unit, showing the arrangement of the primary circuitconductors at that point.

Figs. 17, 18, and 19 are plans of the insulator blocks at the lower endsof the three primary circuit turns.

Fig. 20 is a view of the method of attaching the weight bars to thetransformer structure at the lower end of same below the insulator blockshown in Figs. 15 and 19.

The combination of parts numbered on the drawings as 12, 14, 16, 1'7,18, 19, and 35, together with the necessary minor accessories arereferred to in a general way in this specification and claims as thestufling box structure.

The combination of parts shownon Figures 4 5, 6, 7, 8, 9, 10, 11, and 15are referred to in a general way in this specification and claims as thetransformer structure or transformer column.

The clamps numbered 20 and 21, and the rams numbered 23 and 27 on thedrawings, together with their operating accessories and minor details ofconstruction are referred to in a general way in theclaims as clamps andrams and means for operating same.

Referring to Fig. 1, an alternating current generator 1 supplies currentthrough the switch 2 to the supply transformer 3, shown in conventionalmanner indicating a transformer with regulator in the primary circuit.The secondary circuit of this supply transformer is connected through aswitch 4 to the terminals of the well service cable 5, situated atconvenient points on a drum 6, upon which the well service cable iswound for transportation, and unwound for delivery over the second drumor wheel '7 to the Well head. The drum is provided with means forsteadily turning on an axle to wind up or unwind the cable, and a brakeon a side drum 8 for safety in unwinding. The diameters of the drums 6and 7 are made large enough to carry the cable 5 and the welltransformer column which is suspended'from the cable. These drums withtheir supports and appurtenances may be designed in accordance withordinary practice in large cable Work and mine winding gear.

The cable and transformer column have to be inserted into the wellagainst gas pressure, and therefore special means'are provided foraccomplishing this operation. In the first place the well head 9 isprovided with a stop valve 10 above the gas and oil outlet 11. Above thestop valve there is provision for two stuifing boxes, one box 12 suitedto the diameter of the transformer column 13 (Figs. 2, 12, 13 and '15)and the other box suited to the smaller diameter of the service cable 5.

It is intended that the gas should be carried off through the outlet 11to some convenient point of discharge at the time of inserting theapparatus, and should have sufficiently large area of passage to bringthe gas pressure at the well head down toa low figure to permit theconvenient insertion of the heater. If necessary a second outlet shouldbe provided in addition to the ordinary service outlet. The transformercolumn is necessarily a flexiblestructure when made to wind on a largedrum, and needs special treatment while being inserted through thestuffing box against the gas pressure. This can be' done partly bysuspending rigid weight bars below the transformer column, and partly byspecial clamps to grip the column in line with the well, and force itdown through the stuffing box in a perfect straight line. Part of thefirst weight bar can be put through the stuiiing box 12 while the stopvalve is closed. A small pipe 15 is provided below the stufiing box,through which wax or thick grease may be injected under pressure, toassist in making the packings gas tight. The casting 16 (Figs. 1 and 2)serves as the gland for the stuffing box 12 and also as the socket ofthe stufiing box 14 when a cup shaped liner 17 is inserted to make thestufiing box 14 a smaller diameter than 12. This cup shaped liner 17 andthe cup leather packings are made in halves to assemble round the cable5. v

Before the liner 17 is put in place and while the weight bars andtransformer column are being inserted, another casting 18 (Fig. 1) alsomade In halves, is placed in the socket of gland 16 and has extensionsupwards to form a holder 19 for the flanges at the bottom of the lowerclamp 20. These flanges serve to prevent the suspended weight bars ortransformer from sliding down or being blown up by gas pressure when theclamp 20 is screwed up, or pressed tight to grip the suspended bars ortransformer. Another clamp 21 (Figs. 1, 12, 13 and 14) is providedhigher up, and is carried on a crosshead 22 which is attached to tworams 23 working in four outside-packed oil pressure cylinders 24. Theclamp 21 is shown roughly in Fig. 1, and more in detail inFigs. 13 and14. Fig. 14 shows, above its centre line, a half plan on top of theupper clamp mechanism, and below its centre line, a half sectionalplanthrough the centre of the clamp at lines 14, 14, of Figs. 12 and 13. Thegripping part 21 is made in six segments with rubber or other suitablegrip facings dovetailed into the castings and having small clearancespaces at the segment joints. The segments have conical taperedshoulders 25 engaging in corresponding cone recesses in two collars 26which can be pulled together vertically; by two oil pressurerams 27 (oneof which appears on Figs. 12 and 14) and pushed apart by springs 28 whenthe oil pressure is released.

The collars 26 are made in halves and bolted together by the bolts 29,and are constrained to move concentrically with the stufiing boxes belowby having turned projections 30 engaging in corresponding turnedrecesses in the crosshead 22, which is moved rigidly in line by the rams23. The supports for these rams in relation to the well head, and otherdetails, are omitted from the drawings for the sake of clearness, asthey are only matters of ordinary structural design.

In Figs. 12 and 13 the clamp segments 21 are extended upwards anddownwards through the crosshead, and have flanges 31 abutting on turnedsurfaces on the crosshead, which flanges carry the upward or downwardthrust m suspended weight. Oil under pressure from a suitable source issupplied to, and discharged from the cylinders 24 (Fig. 1) throughthree-way valves 32 and through a similar valve and flexand transformeris to grip the lower clamp while setting the upper clamp at the top ofits stroke, then grip by the upper clamp, release the lower clamp, andby regulating the oil valves 32, lower the rams 23 with their load tothe end of the down stroke, then grip the lower clamp again whilere-setting the upper clamp at the top of the next stroke. The brake drumon the cable drum 6 (Fig. 1'.) is a safety appliance as a security incase of a clamp slipping. When all the weight bars and transformersections have been inserted in the well, it becomes necessary to connectup the well service cable 5.

The joint for this is shown on Fig. 4 and described later on. As the,cable5 is of smaller diameter than the transformer, the stuffing box Thelower 14 must be completed. To do this, the upper clamp is refitted witha different set of gripping segments to suit the smaller diameter, andthen gripped to hold the weight while the lower clamp is similarlyrefitted, and also the casting 18 is replaced by a similar one with itsinside diameter and lower end extension suited to fit as a gland to thestufling box 14 after the liner 1'? and the cup leathers have been putin. This operation is done while the tapered joint of the cable 5 to thetransformer column 13 is held as shown in Fig. 2, with the largerdiameter filling the stuffing box 12. The lowering operations can thenbe continued as before, and if the weight of the material alreadyinserted is not then more than sufficient to balance the gas pressure onthe area of the throat of the stufling box 12 it will generally do soimmediately on the reduced area of the box 14, and then the lowering maybe done by the more rapid method of turning the drum 6 and using thebrake 8. When the correct depth has been reached the lower clamp andcasting 18 are again dismantled and the holding clamp 35 shown at thetop of Fig. 2 and in plan on Fig. 3 can be put in to hold the cable inplace. Packing blocks or plates can be put under the flanges of theclamp 35 and the casting 16 to keep the weight of! the gland packings.

Figs. 4, 5, and 6 illustrate the construction of the connection betweenthe well service cable 5 which has a pair of conductors, and thetransformer structure below, which requires several turns of theseconductors to make up the primary circuit of the transformers and willbe better understood after explaining the structure of the transformersillustrated in Figs. '7, 8, 9, and 11. The lower end of Fig. 1 shows aschematic diagram of the arrangement of the electric transformers withthe primary circuits 36 in series, and the secondary internal circuits37 connected to a common network of external heating circuits 38,putting all the secondary circuits in parallel in accordance with theconstruction shown in Figs. '7, 8, 9, 10 and 11. Only three transformersections or units are shown in the diagram, but in practice there willusually be a much larger number, and sometimes several hundred.

The network is continuous all round the circumference of thetransformers and is connected to the terminals 39 of the internalcircuits at points diametrically opposite to each other.

In Fig. 1 the two portions of the network 38 shown on the right and leftof the transformers are supposed (for illustration purposes) to beunfolded from quadrants of the circumference and to be actuallyconnected together at the neutral points 40. The other two quadrants ofthe network are omitted from Fig. 1. In the construction shown in Figs.7, l0 and 11, the neutral points 40 of the network are also connected tothe neutral points of the internal circuits by the bars 41 passingthrough the structure and riveted to the lower ends of the internalcircuits by the rivets 42. This item of construction is only for thepurpose of strengthening the tie between the network and the transformerand has no electrical significance. The internal secondary circuit isconstructed as a forging or casting in two parts, meeting along the line43 in Fig. 11 (which is a plan of the lower end) to enable the parts tobe assembled from opposite sides of the continuous primary circuitconductors 36, and those two parts are held together by the bars 41 andrivets 42 and also by the rivets 44 shown in Figs. 7 and 10.

Electric welding might be used to join these two parts of the secondarycircuit 37. An elevation of part of the external secondary circuitnetwork is shown in Fig. 9. The crosses on this figure show the spotswhere the wires are welded together and to the terminals 39 of theinternal secondary circuit and to the rings 46.

Fig. 10 shows a plan of one terminal 39 at the top of the internalsecondary circuit in relation to the external network 38 and to the bar41 which is riveted to the lower (or neutral) end of the next unitabove. For the sake of preserving the alignment of the meshes of thenetwork 38 and to tie them into the transformer, a semicircular bar 45is welded on to each side of the bar 41 at the points marked by crossesin Fig. 10 which are always neutral points in the circuit.

The bars 45 are wrapped with asbestos insulation along the rest of theirlength, and split metal rings 46 are turned round the bars 45 andelectrically welded to successive points on the network 38, which aresubject to fluctuation of potential above and below the neutral point.For instance, the first ring may fluctuate /2 a volt above and below theneutral, the second ring 1 volt, the third 1%; volts and the fourth ring2 volts at the point where it joins the network 38 and also the terminalof the internal circuit 39. The voltage on the opposite side of thecentre line will vary in the same proportion in the other direction,making a total difference at the terminals of the internal circuit fourvolts in the case assumed for illustration.

In Fig. '7 the horizontally shaded parts 47 represent the laminated coreof the transformer, and in Figure 8 the shape of the sheets is shown inthe unshaded area 47, these sheets being assembled from opposite sidesof the primary and secondary internal circuits and overlapped at theirjoints 48 in the usual way. A dot and dash line 49 indicates theapproximate centre of the lines of magnetic flux. The core is in generalharmony with ordinary transformer practice, except that shellac andpaper are not used, on account of the temperature being liable to damagethose materials. Asbestos and mica sheets are used to insulate the edgesof the laminated core where it adjoins the secondary circuit at 50 andbetween the core and the network 38 at 51. Shields of steatite may beplaced in the diamond mesh spaces of the network as shown in elevationat 52 in Fig. 9, and in plan on Fig. 8. Another piece of steatite isplaced at 53 (Fig. 7) on top of the centre section of the core and underthe bar 41. All other spaces between the parts of the transformersalready mentioned are filled with asbestos, talc, or other insulatingmaterial not liable to become charred, and which can be easily packedand afterwards impregnated with oil. The primary circuit conductors 36are insulated with asbestos in several layers to provide insulationsuitable for 1000 volts or sometimes more.

Fig. 8 shows three turns of the primary circuit l and one secondaryturn. It will be readily understood that the planning of these circuitsis amenable to variations without altering the main feature of theinvention, which is the combination of a primary circuit in seriesthrough a number of separate transformer units with the secondaryinternal circuits, generating a very low voltage current, delivered toseparate or parallel external circuits, and all built up in a column orcable suitable for suspension in a gas well. Any

' not used, but a second block of the same pattern aiteratio'nofgrouping of the parts 6f the transformer units which does not changetheir functions, and is within the scope of known practice in ordinarytransformer construction, is intended to be included as a possible partof this invention. Another point capable of variation is the featuredescribed for holding the network by the bars 45 and rings '46. This isdesigned to suit the cases where it is'desired to keep the transformerunits close together.

In some cases this is not necessary, and if the are spaced a few inchesapart, the network wires can be bent inwardly and bound tight in arecess of a reel shaped block of insulating porcelain, silica, orsteatite, such as shown on Figs. l5 and 16 at 72, by somebinding wirewith insulating material inserted over the network to prevent shortcircuiting the wires.

Having described the arrangement of primary conductors in the units ofthe transformers with three turns, the features of Figs. 4, 5 and 6 willbe more clearly understood. The service cable 5 shown at the top of Fig.4 may be a twin conductor cable, insulated for 1000 volts or more, withmaterial not necessarily suited to high temperatures, but not usingrubber or other material liable to deteriorate when exposed to oil,unless protected by lead sheathing. The cable must, however, have avery'strong external armouring of steel wire or tape in one or morelayers, to bear the tensile stresses of suspension in the well.

This service cable is therefore not usually suitable for extensionthrough the transformers as a primary circuit, and is therefore jointedto the primary circuit as shown in these figures. The twin conductorsfrom 5 are spliced to the terminals of the transformer primary at 54 inFig. 4, where one conductor is behind the other as shown in Fig. 5,which is a plan on top of a porcelain, silica or glass block 55 havingholes for the passage of conductors, one pair of holes 56 having aconnecting slot 5'7 near the top of the block with a semi-circularbearing for one conductor to turn over from one hole 56 to the otherhole 56. This is the support for one pair of the primary circuitconductors, the insulated conductor being stripped bare to pass upthrough the block, over the bearing and down the other hole to bespliced to another insulated conductor below the block. The third pairof holes shown in Fig. 5 is is placed a little lower down with thesituation of the slotted pair of holes reversed, as shown in Fig.

6, to receive the next turn of the primary circuit at 58, while the turnwhich passed at 56 in Fig. 5 is spread to 59 in Fig. 6. Thisconstruction is adopted to give ample space to make the splice as at 60in Fig. 4 without having another splice side by side, and to have theturn in the slot plugged with insulating material and ample space tomake the insulation good for several hundred volts. The blocks 55 haverecesses 55a on the outside circumference into which the suspendingwires are bent and held by binding wires. Below the second block Fig. 6the six conductors are re-arranged into parallel plan shown in Fig. 8

and the intervening spaces packed with insulation. The wire armouring 61of the cable 5 is bent back over a tapered thimble 62 and gripped inthat position by the network wires from below "being turned over asimilar thimble 63 tapered segments of steatite 65 are inserted betweenthe thimble 62 and the block 55. The first, or uppermost unit of thetransformer, below the primary suspension'block 55, is placed at asufficient distance to give a network resistance, from the top of thetransformer terminals to the block 55, not less than thenormalresistance on the zig-zag mesh circuit from the terminals to theneutral point. A similar precaution is taken below the lowesttransformer to the porcelain blocks 66, 6'7 and 68 (Fig..15) whichprovide turning points for the three pairs of primary conductors (shownin dot and dash lines) with space for splices 69, 70 and 71, and slotsfor the turns arranged as shown in the plans of the blocks 66, 6'7 and68 in i7, 18, and 19. Another porcelain block '72 may be used (Figs. 15and 16) below the bottom transformer unit with an insulating bindingover the network of the same kind as used for the alternative bindingbetween the transformers when there is room for that construction.

, Three of the lowest transformer units are indicated on Fig. 15 by theU shaped internal secondary circuits 37.

Below the block 68 comes the terminal metal fork 73 Fig. 20., to whichthe weight bars '74 are attached by pins '75. The metal fork has a neckinto which the networkwires are bent and bound at 76. The weight barsare preferably solid and have holes 77 and flats '78 provided tofacilitate handling at the well head. The whole of the transformersection may be impregnated with oil, and also bound up in tarred fabricfor protection in transportation and insertion to the well. When theheat is applied the tar will melt oif and the fabric disintegrate,leaving the network 38 directly exposed to the gas and oil spray.

The normal condition in operating the apparatus is to regulate thevoltage at the supply transformer 3 (Fig. 1) to obtain a temperature ofthe gases issuing from the well with a margin of a few degrees abovefreezing point.

Various details of the construction, as hereinbefore described andillustrated in the drawings may be modified without departing from thescope and intention of the invention, the novel features of which Iclaim as follows:

1. In a natural gas well suspended heater operated by electricity, thecombination of a multiple system of alternating transformers arranged ina' vertical column with the high voltage primary circuit placed inpassages surrounded by the laminated iron cores of a plurality oftransformer units, and said primary circuit passing in series throughsaid units and bending over insulating blocks at the top and bottom ofsaid column to form turns in the circuit, each transformer unit having aseparate internal secondary circuit with the active portions placed inthe same passages through the cores, and having terminals brought to theoutside circumference of said cores, and there connected to the externalheating circuits assembled round the said transformer units.

2. In a natural gas well suspended heater operated by electricity, thecombination of a multiple system of alternating current transformersarranged with the high voltage primary circuit passing in series througha plurality of transformer units having their internal secondarycircuits separate from one another, and arranged to supply a low voltagecurrent to external heating circuits, forming part of the combination,assembled round the said transformer units, and combined with a stufiingbox structure at the well head, to prevent the escape of gas at thatpoint, and mechanical devices consisting of clamps to grip thetransformer structure and suspending cable, and rams to force the saidstructure and cable through the stuffing box structure, and means ofsuitable type for operating the said clamps and rams to insert the saidtransformer structure and suspending cable into the well against a gaspressure.

3. In a natural gas well suspended heater oper ated by electricity, thecombination of a multiple system of alternating current transformersarranged with the high voltage primary circuit passing in series througha plurality of transformer units having their internal secondarycircuits separate from one another, and arranged to supply a low voltagecurrent to external heating circuits, forming part of the combination,assembled round the said transformer units, and combined with a stuffingbox structure at the well head, to prevent the escape of gas at thatpoint, and mechanical devices consisting of clamps to grip thetransformer structure and suspending cable, and rams to force saidstructure and cable through the stuffing box structure, and means ofsuitable type for operating the said clamps and rams to insert the saidtransformer structure and suspending cable into the well against a gaspressure, and combined with weig t bars attached to the lower end of thesaid transformer structure to assist the process of insertion of thesaid transformer structure and suspending cable through the saidstuffing box against the gas pressure.

4. In a natural gas well suspended heater operated by electricity, thecombination of a multiple system of alternating current transformersarranged with the high voltage primary circuit passing in series througha plurality of transformer units having their internal secondarycircuits separate from one another, and arranged to supply a low voltagecurrent to external heating circuits, forming part of the combination,assembled round the said transformer units, and combined with a stuffingbox structure at the well head, to prevent the escape of gas at thatpoint, and mechanical devices consisting of clamps to grip thetransformer structure and suspending cable, and rams to force saidstructure and cable through the stuffing box structure, and means ofsuitable type for operating the said clamps and rams to insert the saidtransformer structure and suspending cable into the well against a gaspressure, and combined with weight bars attached to the lower end of thesaid transformer structure to assist the process of insertion of thesaid transformer structure and suspending cable through the saidstuffing box against the gas pressure, and combining the feature ofhaving the external secondary circuits of the transformer unitsconnected in parallel as a network of wires assembled round thetransformer structure and while acting as the heating elements in directcontact with the gas, also serving as a suspending support to the saidstructure.

E. C. THRUPP.

